Drill chucks

ABSTRACT

A chuck for drills and the like including at least three jaw elements of tapered form connected to a jaw carrier by means of flexible elements. Means are provided for urging the jaw elements axially relative to a nose cone so that they act against a frusto-conical bore portion of said nose cone and are urged radially inwards, accompanied by flexing of the flexible elements, to grip the shank of a drill or the like.

The invention relates to drill chucks and has for its object to providean improvement therein.

According to the invention, a drill chuck is provided with three or morejaw elements connected by means of flexible elements to a jaw carrier,said jaw elements being of tapered form and being arranged to bearagainst a frusto-conical portion of a bore of a nose cone, means beingprovided for urging said jaw elements axially relative to said nose coneso that the jaw elements are urged radially inwards, accompanied byflexing of the flexible elements, to grip the shank of a drill bit whichhas been placed in the chuck. The flexible elements may be made of asynthetic plastics material and may be moulded integrally with the jawelements. Alternatively, said flexible elements may be made of springsteel and provided with means whereby they can be "snap-fitted" orotherwise connected to the jaw elements. The jaw elements, when made ofa synthetic plastics material or cast in soft metal, may be providedwith hard metal inserts which will engage a drill shank carried by thechuck.

The required relative axial movement between the jaw elements and thenose cone may be effected by screwthreaded adjustment of the latteralong a screwthreaded portion of the jaw carrier, and in this case theflexible elements may be formed integrally with said jaw carrier or maybe releasably connected thereto, conveniently by "snap-in" connectionmeans at the ends of the flexible elements remote from the jaws. Thescrewthreaded adjustment of the nose cone along a screwthreaded portionof the jaw carrier may be facilitated by a tommy-bar capable of beingfitted in at least one radial hole provided in the nose cone, or by apair of tommy-bars capable of being fitted in respective radial holesprovided in the nose cone and in the jaw carrier. Alternatively, thescrewthreaded adjustment of the nose cone along a screwthreaded portionof the jaw carrier may be facilitated by a ring spanner capable of beingengaged with a non-circular exterior portion of the nose cone, or by apair of ring spanners capable of being engaged with respectivenon-circular portions of the nose cone and of the jaw carrier.Conversely, the screwthreaded adjustment of the nose cone along ascrewthreaded portion of the jaw carrier may be facilitated by a gearedkey a pilot portion of which is capable of being engaged with a radialhole in the jaw carrier or in a part carried by said jaw carrier, saidgeared key being capable of being engaged with the teeth of a gearedring formed integrally with or connected to the nose cone. In this casea plurality of radial holes may be provided in the jaw carrier forengagement by the pilot portion of the geared key, said holes beingarranged helically around a cylindrical portion of the jaw carrier sothat an appropriate one of said holes can be selected for engagement bysaid pilot portion of the geared key according to the axial location ofthe geared ring along said jaw carrier when a final tightening of thejaw elements on the shank of a drill bit is to be effected.Alternatively, a slidable element may be provided in a longitudinallyextending slot in a cylindrical portion of the jaw carrier, saidslidable element being provided with a hole radial to said jaw carrierfor the reception of the pilot portion of the geared key, and the axiallocation of the slidable element along its slot being controlled by theposition of the geared ring along the jaw carrier so that the properengagement of the teeth of said geared key with the teeth of the gearedring is maintained. Conversely, a cam-like collar element may surround acylindrical portion of the jaw carrier and abut at one side against aninclined shoulder having a plurality of radial notches formed on saidjaw carrier, said collar element being provided with the hole in whichthe pilot portion of the geared key can be engaged, the arrangementbeing such that said collar element can be appropriately positioned,with a projection with which it is provided engaging a selected one ofthe notches in the inclined shoulder of the jaw carrier, so that whenthe jaw elements have been urged axially relative to the nose cone adistance sufficient to bring them into engagement with the shank of adrill bit which is to be gripped, the geared key can be applied to thechuck to effect the final tightening. The screwthreaded portion of thejaw carrier may be formed as a sleeve snapped on a spigot portion of thecarrier and secured thereon against rotation.

Alternatively, the required relative axial movement between the jawelements and the nose cone may be effected by a screwthreaded drivingspindle of a power tool being screwed through a screwthreaded bore of anend plug on which the cone is secured whereby an end face of saiddriving spindle abuts against and axially displaces the jaw carrier towhich the flexible elements are connected or with which they have beenintegrally formed.

In a further construction, the relative axial movement between the jawelements and the nose cone may be effected by means of a sleeveencircling a generally cylindrical skirt portion of the nose cone andhaving screwthreaded engagement therewith, said sleeve being capable ofimparting axial movement to the jaw carrier within the skirt portionthrough axially extending slots in said skirt portion. In this case, thejaw carrier may be provided with key elements extending radiallyoutwards through the slots in the skirt portion of the nose cone, aconnection being established between said key elements and the sleeve sothat the latter can rotate relative to the jaw carrier, and thescrewthreaded connection between the sleeve and the skirt portion of thenose cone may be by way of circumferentially spaced and axiallyextending threaded spline portions, the arrangement being such that whena drill bit has been entered into the chuck the sleeve element can firstbe slid forward along the skirt portion of the nose cone, with thethreaded spline portions of each out of engagement, so that the jawelements are brought into engagement with the frusto-conical portion ofthe bore of the nose cone and thus moved radially inwards to lightlygrip the surface of the shank of the drill bit, and then the sleeveelement can be turned to bring its threaded spline portions intoengagement with the threaded spline portions of the skirt portion of thenose cone whereby a tight locking action can be applied to provide atight grip of the jaw elements on the shank of the drill bit.

In order that the invention may be fully understood and readily carriedinto effect, the same will now be described, by way of example only,with reference to the accompanying drawings, of which:

FIG. 1 is a part-sectional view of one form of drill chuck embodying theinvention,

FIG. 2 is an exploded view thereof, and

FIG. 3 is a view in the direction of arrow 3 in FIG. 2, that is to sayan end view of one of the components of the chuck,

FIG. 4 is a view similar to FIG. 1 of a modified form of chuck embodyingthe invention,

FIG. 5 is an exploded view thereof, and

FIG. 6 is a sectional view on the line 6--6 in FIG. 5,

FIG. 7 is a further view similar to FIG. 1 and illustrating a furthermodified form of chuck embodying the invention, and

FIG. 8 is an exploded view thereof,

FIG. 9 is a still further view similar to FIG. 1 and illustrating astill further modified form of chuck embodying the invention, and

FIG. 10 is an exploded view thereof,

FIG. 11 is a part-sectional view illustrating a possible modification ofthe chuck shown in FIGS. 9 and 10,

FIGS. 12 and 13, FIG. 14, FIGS. 15 and 16 and FIGS. 17 to 19 are viewswhich will presently be referred to when describing further possiblemodifications of the chuck shown in FIGS. 9 and 10,

FIG. 20 is yet a further view similar to FIG. 1 and illustrating afurther modified construction, and

FIG. 21 is an exploded view thereof,

FIG. 22 is a view similar to FIG. 1 but illustrating a rather differentform of chuck embodying the invention, and

FIG. 23 is an exploded view thereof,

FIG. 24 is a part-sectional view illustrating a modification of thechuck shown in FIGS. 22 and 23, and

FIG. 25 is an exploded view thereof,

FIG. 26 is a part-sectional view illustrating a very different form ofchuck embodying the invention,

FIG. 27 is an exploded view thereof,

FIG. 28 is a sectional view on the line 28--28 in FIG. 27,

FIGS. 29 and 30 are sectional views on the lines 29 -- 29 and 30 -- 30respectively in FIG. 28, and

FIGS. 31 to 36 are further views which will be referred to whendescribing further possible modifications.

Referring now to FIGS. 1 to 3 of the drawings, the drill chuck thereillustrated includes a jaw carrier 10, four equally spaced jaw elements12 connected by means of flexible elements 14 to said jaw carrier, and anose cone 16 a screwthreaded bore portion 18 of which engages ascrewthreaded portion 20 of the jaw carrier. The chuck also includes acombined end plug and mount generally indicated 22 which is force fittedin the hollow interior of the jaw carrier from its end remote from thejaw elements, a splined connection being provided between the two partsso that full driving torque can be transmitted from the mount to the jawcarrier. The mount is provided with a threaded bore 24 for the receptionof a power tool driving spindle (not shown). At its end which is locatedwithin the jaw carrier, the end plug and mount 22 is dimpled at 26 toprovide a centering location for an end of a drill bit which is to beheld in the chuck.

As best seen in FIG. 2, the jaw elements are of tapered form and arearranged to bear against a frustoconical portion 28 of the bore of thenose cone. The arrangement is such that when the jaw elements are urgedaxially relative to the nose cone, by the screwthreaded adjustment ofthe latter along the screwthreaded portion of the jaw carrier, the jawelements are urged radially inwards to grip the shank of a drill bitwhich has been placed in the chuck. The radially inward movement of thejaw elements is of course allowed by the flexing of the flexibleelements 14, and when the nose cone is subsequently slackened, that isto say backed off the screwthreaded portion of the jaw carrier, theflexible elements are then able to assume their former condition andre-open the jaw elements.

In this embodiment the jaw carrier 10 has been moulded in a syntheticplastics material, integrally with the flexible elements 14 and with thejaw elements 12 (and it will be seen in FIGS. 2 and 3 that each jawelement has in this instance been provided with a moulded-in metalinsert 30 of triangular cross section). However, it is not essentialthat all the component parts should be made of plastics or that the jawcarrier, flexible elements and jaw elements should be formed integrallytogether as will become more apparent from the further descriptionconcerning modified forms of drill chucks embodying the invention. Tofacilitate the tightening and untightening of the chuck the outersurface of the nose cone and the periphery of the jaw carrier are shownto have been given a fluted form (but it will be understood that thesecould equally well have been knurled, or moulded with a knurled externalappearance for example, to provide the required non-slip hand grip).

Referring now to FIGS. 4 to 6, in a modification of the chuck describedabove the jaw carrier 10 has been moulded integrally with a portionconstituting a dimpled end stop 32 and has also been formed with thethreaded bore 24 for the reception of a power tool driving spindle. Inthis case however, the jaw elements 12, which have been mouldedintegrally with the flexible elements 14, have been formed separate fromthe jaw carrier, but means have been provided whereby they have beenable to be connected thereto by "snap-in" connection means constitutedby a radially lipped ring part 34 moulded integrally with the flexibleelements and an undercut annular cavity 56 formed in an end face of thejaw carrier for the reception of said ring part. A further modificationwhich will be observed in this case is that guideways 17 extend alongthe frustoconical portion of the bore of the nose cone. These supportthe jaw elements as the latter are displaced relative to said nose coneand the jaw elements are restrained against "toggle" action. (The jawelements are able to be guided in this way in this particular case byvirtue of the fact that as the nose cone is rotated, the radially lippedring part 34 with which the jaw elements are connected is able to rotatein the cavity 36 formed in the jaw carrier).

In FIGS. 7 and 8 there is illustrated a form of chuck very similar tothat just described except that the means whereby the jaw elements andintegrally formed flexible elements have been able to be connected tothe jaw carrier are rather different. In this case the jaw carrier 10 isprovided with a circumferential groove 38 and the flexible elements aremoulded integrally with an internally lipped ring 40, the latter being asplit ring so that its lip is able to be engaged in the groove in thejaw carrier, being retained therein as the nose cone is engaged with thescrewthreaded portion of the jaw carrier. The arrangement is such thatthe jaws and the flexible elements can rotate relative to the jawcarrier as screwthreaded adjustments of the nose cone along thescrewthreaded portion of the jaw carrier are made. Consequently, theflexible elements are safeguarded against twisting and the jaw elementsare safeguarded against "toggle" action. (It will be understood that, ifpreferred, the jaw elements could in this case also be located inguideways in the nose cone).

Referring now to FIGS. 9 and 10, in a different modification of thefirst described embodiment the jaw carrier is a two-part member, beingformed in part by a member generally indicated 42, which includes thethreaded bore 24, and in part by a screwthreaded sleeve 44 which ismoulded integrally with the jaw elements 12 and the flexible elements14. The sleeve 44 is a snap fit on a spigot portion 46 which has beenmoulded integrally with the member 42, the two parts having been formedwith snap ring and groove portions indicated 48 and 50 respectively andwith co-operating key and slot portions indicated 52 and 54 respectivelyby means of which they are secured against relative rotation. Whenassembled, this form of chuck can be operated in the manner of the chuckillustrated in FIGS. 1 to 3 and the end face of the spigot portion 46 ofthe member 42 acts as an end stop for the abutment of the shank of adrill bit.

Referring now to FIG. 11, in a modification of the chuck just described,the fluted exterior surfaces of the nose cone and of the jaw carrierhave become plain cylindrical surfaces except for the provision of anumber of radial holes 19 in each. A pair of tommy-bars 21 are shown tobe provided and are capable of being fitted in respective holes in saidnose cone and jaw carrier for the purpose of facilitating thescrewthreaded adjustment of the nose cone along the screwthreadedportion of the jaw carrier. (It will of course be understood that, ifpreferred, the nose cone alone could be provided with the series ofradial holes or that only a single tommy-bar be provided to be usedinitially for very tightly fixing the jaw carrier on the driving spindleof a power tool and subsequently for turning the nose cone when theshank of a drill bit is to be held by the chuck).

In FIGS. 12 and 13 there is illustrated a different and perhapspreferable way of achieving the same object, a pair of ring spanners 23being provided for engagement with the fluted exterior shape of the nosecone and jaw carrier. In this way the facility of convenient handtightening prior to the final tightening by the ring spanners isretained. (Here again it will be understood that, if preferred, a singlesuch ring spanner could be provided. It will also be understood that thenose cone and jaw carrier could be of any other non-circular exteriorshape, the ring spanner, or each ring spanner, as the case may be, thenbeing of complementary shape).

Referring now to FIG. 14, this illustrates a construction of chucksimilar to that illustrated in FIGS. 9 and 10 but in which thescrewthreaded adjustment of the nose cone along the screwthreadedportion of the jaw carrier is facilitated by a geared key, generallyindicated 172, a pilot portion 174 of which is capable of being engaged,as shown, with one of a plurality of radial holes 176 in the jaw carrierand gear teeth of which are capable of being engaged, also as shown,with the teeth of a geared ring 178. The geared ring is connected to thenose cone 16, as shown, by a snap-in connection indicated 180constituted by an inturned flange portion of the nose cone and a groovein the geared ring component. In addition, a key and slot connectionindicated 182 is provided to lock the two components together againstrelative rotation when the chuck is tightened.

It will be observed that the holes 176 are arranged helically around acylindrical portion of the jaw carrier. This is so that an appropriateone of said holes can be selected for engagement by the pilot portion ofthe geared key according to the axial location of the geared ring alongsaid jaw carrier when a final tightening of the jaw elements on theshank of a drill bit is to be effected. An initial adjustment to bringthe jaw elements into engagement with the shank of the drill bit can ofcourse be effected by hand.

Referring now to FIGS. 15 and 16, the chuck there illustrated isbasically similar to that just described except that instead of theplurality of radial holes 176 in the cylindrical portion of the jawcarrier the latter has been provided with a longitudinally extendingslot 184 in which a slidable element 186 has been fitted. The element186 is provided with a hole 188 which is radial to the jaw carrier forthe reception of the pilot portion 174 of the geared key 172. Anundercut circumferential groove within the geared ring receives a raisedlip 190 at one end of the slidable element 186, as shown, so that thegeared ring is allowed to rotate but carries with it, as it moveslongitudinally, the slidable element 186 so that the proper engagementof the teeth of the geared key with the teeth of the geared ring isconstantly maintained.

In FIGS. 17 to 19 there is illustrated another construction which isbasically similar to that described with reference to FIG. 14, but inthis case instead of the plurality of radial holes 176 in thecylindrical portion of the jaw carrier the latter is surrounded by acam-like collar element 192 which abuts at one side against an inclinedshoulder formed on said jaw carrier, the collar element being providedwith the hole in which the pilot portion 174 of the geared key 172 canbe engaged as shown. The collar element is also provided with aprojection 194 which can be engaged with a selected one of a pluralityof radial notches 196 formed in the inclined shoulder of the jawcarrier, and the arrangement is such that when the jaw elements havebeen urged axially relative to the nose cone a distance sufficient tobring these into engagement with the shank of a drill bit which is to begripped (conveniently by manual rotation of the nose cone) the gearedkey can be applied to the chuck to effect the final tightening and theteeth of the key will then be found to engage properly with the teeth ofthe geared ring. The radial notches in the jaw carrier are marked sothat the appropriate one can be engaged by the projection on the collarelement according to the size of drill bit which is to be gripped. Thecollar element can be released for re-positioning relative to theinclined shoulder of the jaw carrier by slackening back the geared ringaway from said collar element.

Referring now to FIGS. 20 and 21, there is there illustrated a chuckwhich in some ways is very similar to those previously described withreference to FIGS. 4 to 6 and FIGS. 7 and 8 in that the jaw carrier 10is formed integrally with the screwthreaded portion 20 with which thenose cone has screwthreaded engagement and also in that it is providedwith the threaded bore 24 for the reception of a power tool drivingspindle. However, in this case the jaw elements 12 have been formedseparately from the flexible elements 14 and indeed the latter have beenmade of spring steel strip. Each flexible element is formed at one endwith an inturned portion 56 which can be retained in a slot 58 in an endface of the jaw carrier. At its other end each flexible element has anotch 60, as shown, and the arrangement is such that it can be insertedin a slot 62 in the jaw element which it is to carry and can "snap-lock"therein about a pin element or formation which extends across the slot.

In a rather different form of chuck which is illustrated in FIGS. 22 and23 the operating principle is still the same as in the previousembodiments in that the jaw elements 12 are carried by flexible elements14 and in that means are provided for urging the jaw elements axiallyrelative to the nose cone 16 so that the jaw elements are urged radiallyinwards to grip the shank of a drill bit. However, in this case the nosecone is tightly and permanently screwthreaded onto an end plug 64through which extends the threaded bore 24 for the reception of a powertool driving spindle. The means which are provided for urging the jawelements axially relative to the nose cone so that said jaw elements areurged radially inwards to grip the shank of a drill bit are constitutedby a jaw carrier 66 which is slidably mounted within a cylindricalportion of the bore of the nose cone, said jaw carrier being shown inFIG. 22 in abutment with an end face of the plug 64 but being capable ofmoving away from the end plug to urge the jaw elements axially relativeto the nose cone when acted on by the end of a power tool drivingspindle protruding through the threaded bore 24 of the end plug (andwhen this form of chuck is to be used the power tool driving spindlewill be provided with an extra long screwthreaded portion). The jawelements 12 are moulded integrally with the flexible elements 14 andwith a ring part 68. The jaw carrier 66 has been formed with an annulargroove 70 for the reception of the ring part 68 from which the flexibleelements 14 extend and also with a dimple 26 to provide a centeringlocation for the end of a drill bit which is to be held in the chuck. Itwill be observed that guideways 17 extend along the frusto-conicalportion of the bore of the nose cone as in the embodiment described withreference to FIGS. 4 to 6. These guide the jaw elements along straightpaths as they are urged axially relative to the nose cone (and of coursethey are able to be guided in this way in this particular case by virtueof the fact that tightening is effected without rotation of the nosecone relative to the jaw carrier).

It will be understood that the operation of this form of chuck is ratherdifferent from any of the other chucks previously described in that toopen or close the jaws the whole chuck is rotated upon the power tooldriving spindle (but as previously explained this still results in thejaw elements being urged axially relative to the nose cone). Anadvantage of this form of chuck is that during a drilling operation thetorque applied to the drill bit will tend to tighten the chuck upon thepower tool driving spindle and thus to exert a greater axial thrustagainst the jaw carrier. Consequently, the greater the applied torquethe greater will be the gripping force of the jaw elements on the shankof the drill bit.

The chuck which is illustrated in FIGS. 24 and 25 operates in a mannerexactly the same as that just described with reference to FIGS. 22 and23 but in this case the nose cone is connected to the end plug 64(through which extends the threaded bore for the reception of a powertool driving spindle) by means of a "snap-lock" connection which holdsthem against relative axial movement, that is to say, the nose cone isprovided with an internal ring part 68 and a spigot portion of the endplug is provided with a groove 70 into which said ring part can be snapfitted. A further difference is that the flexible elements 14 whichcarry the jaw elements 12 have in this case been made of spring steelintegral with a portion which forms an internally lipped split ring 72.The jaw carrier 66 is in this case formed with a circumferential groove38 with which the internal lip of the split ring is engaged.

As previously mentioned, this construction of chuck operates in the sameway as that described with reference to FIGS. 22 and 23, that is to say,the whole chuck is rotated on the power tool driving spindle to bringthe end of the spindle into engagement with the jaw carrier and todisplace the latter axially relative to the nose cone.

Referring now to FIGS. 26 to 30, in a very different form of drill chuckembodying the invention the nose cone 16, within a frusto-conicalportion 28 of which the tapered portions of the jaw elements 12 bear, isformed integrally with a parallel bore skirt portion 162 an end ofwhich, remote from the conical part, is provided with a peripheralflange 168. Said peripheral flange of the skirt portion is received in agroove 212 formed within an externally fluted collar 210 which formspart of a mount generally indicated 220 in FIG. 26. Another part of themount is formed by an end plug 222 (formed with a screwthreaded bore 24for the reception of a power tool driving spindle) which is a force fitin the parallel bore of the skirt portion 162 so that it retains thelatter within the collar 210. The flanged end of the skirt portion ofthe nose cone has been able to be inserted within the collar 210 byvirtue of the fact that said skirt portion has a pair of open endeddiametrically opposed slots 166 which have allowed the skirt portion tobe inwardly deformed to bring the flange 164 into engagement with thegroove 212.

The chuck also includes a jaw carrier assembly which comprises the jawelements 12 moulded integrally with the flexible elements 14 and withthe internally lipped ring 40; a carrier member 100 which is formed withoppositely disposed key elements 102; and an externally fluted sleeveelement 104 within which the radially outer portions of the key elementsof the carrier member are secured by means of a circlip 106 so that thesleeve can be rotated relative to said carrier member. The carriermember is provided with a flanged spigot portion which defines acircumferential groove 38 in which the inwardly extending lip of thering 40 (which is a split ring) can be engaged, being retained thereinby the skirt portion of the nose cone as the jaw elements are passestherethrough into engagement with the frusto-conical portion 28 of itsbore. As the jaw elements and integrally formed flexible elements slidealong the bore of the skirt portion of the nose cone, the key elements102 of the carrier member 100 slide along the slots 166 and the sleeveelement 104 encircles the skirt portions.

As shown in FIGS. 27 and 29, the skirt portion of the nose cone isprovided with four circumferentially spaced and axially extendingthreaded spline portions 168 on its outer periphery and these can beengaged by similarly threaded internal spline portions 170 which areprovided, as shown, within the bore of the sleeve element 104 of the jawcarrier assembly.

The arrangement is such that when a drill bit has been entered into thechuck to abut against the end face of the carrier member 100 (which hasbeen formed with a dimple 26 to centre the bit) the sleeve element 104can be slid forwards along the skirt portion of the nose cone, with thethreaded spline portions of each out of engagement of course, so thatthe jaw elements are brought into engagement with the frusto-conicalportion of the bore of the nose cone and thus moved radially inwards tolightly grip the surface of the shank of the drill bit. When no furtherforward movement can be imparted by manual pressure applied axially tothe sleeve element 104, the sleeve element is turned to bring itsthreaded spline portions into engagement with the threaded splineportions of the skirt portion of the nose cone. A tight locking actioncan then be applied to provide a tight grip of the jaw elements on theshank of the drill bit.

Various modifications may be made to any of the drill chucks describedwithout departing from the scope of the invention. For example it willbe understood that although the various drill chucks described abovehave been designed to be manufactured largely of synthetic plasticsmaterials, various component parts could equally well be made of metal.The combined end plug and mount 22 in the chuck illustrated in FIGS. 1to 3 could have been made of metal (and of course would almost certainlybe made of metal if provided with an externally screwthreaded spigotportion for connection to a power tool driving spindle or if providedwith a Morse or similar taper mount). Various other components could bemade as diecastings (but of course if the jaw elements are to be diecastor made of sintered metal or machined from solid metal they will be madeseparately from the flexible elements which carry them, the flexibleelements either being made of spring steel or of a synthetic plasticsmaterial). If the jaw elements are moulded of a synthetic plasticsmaterial (whether integrally with the flexible elements or separatelytherefrom) either the plastics material will be a very hard material orof course the jaw elements will be provided with moulded-in metalinserts as in the case of the chuck illustrated in FIGS. 1 to 3. In thisconnection it will be understood that in any of the chucks described andillustrated the jaw elements could be three or four in number or in factmore than four in number. It will also be understood that a hard metalinsert in a plastics moulded jaw element or in a jaw cast in somerelatively soft metal need not necessarily be of triangular crosssection as shown in FIG. 3. For example, FIG. 31 is an end view of afour jaw moulded part each jaw element being provided with an insert asshown in perspective view in FIG. 32; FIG. 33 is an end view of a fourjaw moulded part each jaw element being provided with a generallycylindrical but longitudinally serrated insert as shown in perspectiveview in FIG. 34; and FIG. 35 is an end view of a four jaw moulded parteach jaw element being provided with an angle section insert as shown inperspective view in FIG. 36. The inserts themselves may be of sinteredmetal or machined from solid metal as preferred. In the chuckillustrated with reference to FIGS. 7 and 8 and in FIGS. 26 to 30 therings 40, with which the flexible elements are moulded, are said to besplit rings. However, it will be understood that, being made of asynthetic plastics material, the rings need not necessarily be splitrings and that they could snap into engagement with the grooves 38. Itwill also be understood that in the case of the chuck described withreference to FIGS. 26 to 30 the screwthreaded connection between thesleeve 104 and the skirt portion 162 of the nose cone need notnecessarily be by way of circumferentially spaced and axially extendingthreaded spline portions. The screwthreads could be full screwthreads(except of course for the diametrically opposed slots in the skirtportion of the nose cone). However, in this case there would be noprovision for quick variation from a very small size of adjustment to amuch larger size and vice versa. Any of the chucks may have provisionfor the attachment of a short bar or key to facilitate the tightening ofthe chuck on a power tool driving spindle or its removal therefrom, oras a means of holding the main body of the chuck against rotation whilstthe user tightens or untightens the chuck by hand as in the case of thechucks illustrated in FIG. 11 and in FIGS. 12 and 13.

It will be understood that in a chuck embodying the invention theflexibility of the flexible elements will be such that throughout itsrange of adjustment the clamping surfaces of its jaws are able to alignthemselves with the axis of the chuck as they bear against the shank ofa drill bit and also that the jaws simultaneously mate correctly withthe frusto-conical portion of the bore of the nose cone.

What I claim and desire to secure by Letters Patent is:
 1. A drill chuckcomprising at least three jaw elements each having a conical taperedexterior surface of diminishing radii in the direction of the endthereof, a jaw carrier; respective flexible elements connecting said jawelements to said jaw carrier, said flexible elements each beingcoextensive in arcuate dimension with the maximum arcuate dimension ofthe conical jaw element to which it is connected; a nose cone having afrusto-conical bore portion; and means for urging said jaw elementsaxially relative to said nose cone so that the jaw elements act againstthe frusto-conical bore portion of the nose cone and are urged radiallyinwards, accompanied by flexing of the flexible elements, to grip theshank of a drill bit placed in the chuck.
 2. A drill chuck according toclaim 1, in which the flexible elements are made of a synthetic plasticsmaterial and are moulded integrally with the jaw elements.
 3. A drillchuck according to claim 1, in which the flexible elements are made ofspring steel and are provided with means for being connected to the jawelements.
 4. A drill chuck comprising at least three jaw elements eachhaving a conical tapered exterior surface of diminishing radii in thedirection of the end thereof, a nose cone; a jaw carrier; respectiveflexible elements connnecting said jaw elements to said jaw carrier,said flexible elements each being coextensive in arcuate dimension withthe maximum arcuate dimension of the conical jaw element to which it isconnected; a nose cone having a frusto-conical bore portion, and meansfor urging said jaw elements axially relative to said nose cone, saidmeans being constituted by screwthreaded adjustment means for adjustingthe nose cone along the jaw carrier, so that the jaw elements actagainst the frusto-conical bore portion of the nose cone and are urgedradially inwards, accompanied by flexing of the flexible elements, togrip the shank of a drill bit placed in the chuck.
 5. A drill chuckaccording to claim 4, in which the flexible elements are releasablyconnected to the jaw carrier by a ring and groove connection means atthe ends of the flexible elements remote from the jaws.
 6. A drill chuckaccording to claim 4, in which said screw threaded adjustment meansincludes cooperating threaded portions on said nose cone and jawcarrier, and at least one radial hole provided in the nose cone wherebya bar can be received in said radial hole to facilitate threadedadjustment of the nose cone along the screw threaded portion of the jawcarrier.
 7. A drill chuck according to claim 4 in which said screwthreaded adjustment means includes cooperating threaded portions on saidnose cone and jaw carrier, and said nose cone is provided with a flutedexterior portion whereby a wrench can engage the fluted portion of thenose cone to facilitate threaded adjustment of the nose cone along thescrew threaded portion of the jaw carrier.
 8. A drill chuck according toclaim 4, in which said screw threaded adjustment means includescooperating threaded portions on said nose cone and jaw carrier, atleast one radial hole is provided in the jaw carrier, and a geared ringis provided on the nose cone, whereby a geared key having a pilotportion capable of being received in the radial hole in the jaw carrierand having gear teeth engagable with the teeth of the geared ringprovided on the nose cone to facilitate screw threaded adjustment of thenose cone along a screw threaded portion of the jaw carrier.
 9. A drillchuck according to claim 8, in which a plurality of radial holes areprovided in the jaw carrier for engagement by the pilot portion of thegeared key, said holes being arranged helically around a cylindricalportion of the jaw carrier so that an appropriate one of said holes canbe selected for engagement by said pilot portion of the geared keyaccording to the axial location of the geared ring along said jawcarrier when a final tightening of the jaw elements on the shank of adrill bit is to be effected.